Imagine your application were filtering seismic vibrations (10 Hz bandwidth) from a sensor in your basement, while the dance club next door is going full tilt. Below a ADAU1452 is simulating the seismic data with a 0.5 Hz triangle wave, adding in the dance music from a MP3 player, then running the resulting mess through an 8-pole Chebyshev LP filter. As we can see, the triangle wave comes through nicely with little disturbance from the music. This sort of performance comes easily in Sigma-land.

Which version of SigmaStudio and which filter cell are you using? SigmaStudio 3.10 and newer should support entering frequencies lower than 20 kHz.

For these lower frequencies of interest, you might also want to run at a lower sample rate (from default 48 kHz) down to 16 kHz or 8 kHz, and consider using the 2nd order double-precision IIR cell. Double precision math can reduce or eliminate any digital filter truncation/round-off noise effects which is worse at lower filter frequencies. However, running the core at lower sample rates will give you the added benefit of more instructions to process the data using double precision math (i.e. 36884 instructions per sample at 8 kHz core rate with 294 MHz clock).

Imagine your application were filtering seismic vibrations (10 Hz bandwidth) from a sensor in your basement, while the dance club next door is going full tilt. Below a ADAU1452 is simulating the seismic data with a 0.5 Hz triangle wave, adding in the dance music from a MP3 player, then running the resulting mess through an 8-pole Chebyshev LP filter. As we can see, the triangle wave comes through nicely with little disturbance from the music. This sort of performance comes easily in Sigma-land.